Mild Behavior: California Tests the Performance of Warm-Mix Asphalt

This article describes a research project conducted by the University of California Pavement Research Center to determine the long-term performance of warm-mix asphalt (WMA) compared to conventional hot-mix asphalt (HMA). The study was aimed at addressing concerns that using the more environmentally WMA will lead to greater amounts of rutting. The author describes the use of a Heavy Vehicle Simulator, a mobile pavement-testing machine that can simulate 20 year of truck traffic in a three-month test. Three WMA technologies are described and were used in the simulation. The researchers discovered the rut depths at the end of the first, or “embedment” phase, were slightly higher for two of the technologies tested. After that phase, however, rutting behavior of WMA sections was similar to the control section. A second round of testing using a constant flow of water across the surface showed that all sections withstood more HVS repetitions before rutting set in. A third round of testing will assess the use of warm-mix technologies with rubberized HMA.